A Comparison of Precipitation Downscaling Procedures to Guide Studies of Climate Change Impacts on Flooding and Water Resources

This was a collaborative project with Dr. Eve Halper from the Bureau of Reclamation (Reclamation), Phoenix Area Office. The project was funded by the Reclamation Science and Technology Grant Program under a cooperative agreement between HRC and the Reclamation Lower Colorado Region (Agreement # R16AC00024).

In recent years, Reclamation and other agencies have been engaged in climate impact assessments of increasingly smaller river basins and local rural communities. The existing methods and datasets that were developed for larger watersheds may not be adequate for arid ephemeral river basins that are often the prevailing landscape of these rural communities. In these relatively small and arid basins, the rainfall characteristics are highly variable and streamflow is tightly associated with the nuances of the rainfall temporal and spatial patterns.

The objective of this research, which is conducted in two arid watersheds in Arizona (the Upper Santa Cruz River watershed and the Bill Williams River watershed) are to:

Evaluate the suitability of various global climate models downscaling methods to produce future projections of precipitation;

Develop a test to decide on the preferred procedure for a given type of study;

Quantify the impact of each method on the Reclamation planning activities.

The study and results are presented in the following documents:

Project Final Report

Shamir Eylon and Eve Halper, Estimating climatic change impacts on water resources in arid environments: the role of downscaling methodology, Research and Development Office, Science and Technology Program, Final Report ST-2019-9039-01. March 2019. Executive SummaryFull Report

Research Bulletin:

Estimating climatic change impacts on water resources: the role of downscaling methodology. Bulletin